The Department of Transportation or DOT, requires marking the date of manufacture on tires. The date is the last four digits (3 prior to 2000) of the alpha-numeric characters, starting with DOT. The first two numbers are the week, and the last two are the year of manufacture. The DOT is on both sides of the tire, but the date code may only be on one side. You may have to check the inside of the tire, depending on mounting.